1. Field of the Invention
The present invention relates to a method for purification of acetone containing at least one oxidizable impurity by contacting the acetone with a heterogeneous oxidation catalyst in the presence of oxygen.
2. Related Background Art
The commercial process for purifying acetone employs a distillation column which separates water and other higher-boiling impurities from the acetone. Traditionally, removal of light aldehyde impurities is accomplished by reactive distillation in which an aqueous solution of sodium hydroxide is injected into the distillation column to promote condensation of aldehydes to form higher-boiling compounds. See, e.g., U.S. Pat. Nos. 5,788,818; 5,567,853; 4,329,510; 3,668,256; 2,906,676; 2,906,675; and 2,624,699. Use of this process requires introduction of water to the distillation column to aid in removing salts and other by-products of the sodium hydroxide reaction. The presence of water, salts, and high-boiling by-products reduces the efficiency of the distillation column.
In particular, crude acetone resulting from the production of phenol from cumene typically contains about 200-700 ppm aldehydes and 200-500 ppm methanol. Treatment of acetone with aqueous sodium hydroxide during distillation leads to production of distillation bottoms containing large amounts of polymers and salts, thereby decreasing the efficiency of conventional reboilers. Moreover, base-catalyzed self-condensation of acetone reduces the yield of purified acetone. Impurity levels in commercial acetone purified by this method are still about 30-50 ppm for acetaldehyde and about 200-300 ppm for methanol. A method for purification of acetone that overcomes the aforementioned difficulties is disclosed herein.
Oxidation of aldehydes and alcohols in the presence of oxidation catalysts is well known in the art. However, applicants are not aware of any attempt to use such a method to purify acetone containing aldehyde and alcohol impurities. The mechanism of oxidation of acetaldehyde, present at high concentrations in various solvents, including acetone, by soluble palladium clusters has been studied by Starchevskiy et al., as reported in Dokl. Akad. Nauk, volume 342, page 772 (1995). However, this study clearly was not directed to a purification method for acetone. Indeed, this reference provides no indication as to whether the soluble palladium catalyst reduced acetaldehyde to ppm levels in acetone, or the extent of acetone decomposition encountered during the oxidation. For these reasons, Starchevskiy et al. do not provide a method that would allow efficient purification of acetone by selective oxidation of impurities.
Applicants are not aware of any use of oxidation catalysts in purification of acetone, despite the commercial quantities of acetone produced worldwide by a variety of processes. An efficient process for purification of acetone would be highly desirable.